S. W. Johnson— Use of Potassium Dichromate. 465 
Hence, anywhere in the gorge of the river, the following 
topographical features are presented: After climbing the pre- 
cipitous walls which closely hedge in the river, and which are 
composed of the Conglomerate series, one is surprised to find 
on surmounting the topmost rim, that he has only attained the 
general level of the country. The river is flowing far below 
im, while around him, and in the distance, rise softly rounded 
hills, plainly showing that he has passed into a series of rocks 
of a physical character very different from those he has just 
left behind. 
The section exposed at Sewell Station does not reach to the 
base of the Conglomerate series, for its lowest strata make their 
first appearance some distance to the east of this point. The 
following is a general description of the strata here exposed. 
The lowest rock visible, a short distance east of the station, is a 
reddish shade. Over this lie some 150’ of a very argillaceous 
and thicker-bedded toward the top. The strata overlying 
them for some 200’ I could not examine in detail, since they 
character, and pass into the massive ledge which forms the 
closing feature in the series. The coals all occur toward the 
middle and top of the series. 
[To be continued. ] 
Art. XLIL—Contributions from the Sheffield Laboratory of Yale 
College. No. XXVIIL—On the Use of Potassium Dichromate 
tn Ultimate Organic Analysis; by S. W. JOHNSON. 
ComBustion of organic bodies by aid of cupric oxide and a 
Stream of oxygen gas, or by the latter alone, as in Warren's 
method, leaves little to be desired when a series of analyses are 
to be executed of substances free from alkali or alkali-earth- 
metals. For occasional use, or for bodies containing the metals 
Just named, recourse is most conveniently had to lead chromate, 
either alone or with admixture of potassium dichromate as 
Liebig suggested. The preparation of lead chromate in a state 
